Mercury iodide (II)

Mercury iodide
Mercury iodide
Are common
Systematic ; name	Mercury iodide (II)
Traditional names	Mercury iodide
Chem. formula	HgI 2
Physical properties
condition	α - red crystals; β - yellow crystals
Molar mass	454.40 g / mol
Density	α - 6,283 ; β - 6.271 g / cm³
Thermal properties
T. melt.	250; 256; 259 ° C
T. bale.	354 ° C
Chemical properties
Solubility in water	0.006 g / 100 ml
Solubility in ethanol	2.19 g / 100 ml
Solubility in methanol	3.16 20 ; 6.51 60 g / 100 ml
Acetone solubility	2.1 g / 100 ml
Classification
Reg. CAS number	7774-29-0
PubChem
Reg. EINECS number
Smiles
Inchi
Chebi
UN number
ChemSpider
Security
MPC	air 0,0003 mg / m³
NFPA 704	0 3 0

Mercury (II) iodide is an inorganic compound, a metal salt of mercury and hydroiodic acid with the formula HgI ₂ , forms crystals of two modifications: α-modification - stable, red crystals, β-modification - metastable, yellow crystals, insoluble in water.

Content

Getting

Rubbing mercury and iodine with a small amount of water or alcohol :

{\mathsf {3Hg+2I_{2}\ {\xrightarrow {}}\ HgI_{2}+Hg_{2}I_{2}}}

{\ displaystyle {\ mathsf {3Hg + 2I_ {2} \ {\ xrightarrow {}} \ HgI_ {2} + Hg_ {2} I_ {2}}}}

The exchange reaction of mercury chloride with alkali metal iodides, a β-modification is formed:

{\mathsf {HgCl_{2}+2KI\ {\xrightarrow {}}\ HgI_{2}\downarrow +2KCl}}

{\ displaystyle {\ mathsf {HgCl_ {2} + 2KI \ {\ xrightarrow {}} \ HgI_ {2} \ downarrow + 2KCl}}}

Decomposition of mercury (I) iodide :

{\mathsf {Hg_{2}I_{2}\ {\xrightarrow {h\nu }}\ HgI_{2}+Hg}}

{\ displaystyle {\ mathsf {Hg_ {2} I_ {2} \ {\ xrightarrow {h \ nu}} \ HgI_ {2} + Hg}}}

Decomposition of potassium tetraiodomercurate :

{\mathsf {K_{2}[HgI_{4}]\ {\xrightarrow {h\nu }}\ HgI_{2}\downarrow +2KI}}

{\ displaystyle {\ mathsf {K_ {2} [HgI_ {4}] \ {\ xrightarrow {h \ nu}} \ HgI_ {2} \ downarrow + 2KI}}}

Physical Properties

Mercury (II) iodide forms several crystalline modifications:

α-HgI ₂ - red crystals, tetragonal syngonium , space group P 4 / nmc , cell parameters a = 0.4357 nm, c = 1.236 nm, Z = 2. Transforms to β-modification at 127 ° С.
β-HgI ₂ - yellow crystals, rhombic syngony , cell parameters a = 0.759 nm, b = 1.380 nm, c = 0.497 nm, Z = 4. Metastable modification.
Orange modification, exists at a temperature above 96 ° C and a pressure of more than 1000 MPa.

Chemical Properties

Decomposed by concentrated sulfuric acid:

{\mathsf {HgI_{2}+2H_{2}SO_{4}\ {\xrightarrow {}}\ HgSO_{4}\downarrow +I_{2}\downarrow +SO_{2}\uparrow +2H_{2}O}}

{\ displaystyle {\ mathsf {HgI_ {2} + 2H_ {2} SO_ {4} \ {\ xrightarrow {}} \ HgSO_ {4} \ downarrow + I_ {2} \ downarrow + SO_ {2} \ uparrow + 2H_ {2} O}}}

Reacts with ammonia solution:

{\mathsf {2HgI_{2}+4NH_{3}\ {\xrightarrow {100^{o}C}}\ (Hg_{2}N)I\downarrow +3NH_{4}I}}

{\ displaystyle {\ mathsf {2HgI_ {2} + 4NH_ {3} \ {\ xrightarrow {100 ^ {o} C}} \ (Hg_ {2} N) I \ downarrow + 3NH_ {4} I}}}

Reacts with hydrogen iodide :

{\mathsf {2HgI_{2}+3HI\ {\xrightarrow {100^{o}C}}\ H[HgI_{3}]+H_{2}[HgI_{4}]}}

{\ displaystyle {\ mathsf {2HgI_ {2} + 3HI \ {\ xrightarrow {100 ^ {o} C}} \ H [HgI_ {3}] + H_ {2} [HgI_ {4}]}}}

With alkali metal iodides forms tetraiodomercurates :

{\mathsf {HgI_{2}+2KI\ {\xrightarrow {}}\ K_{2}[HgI_{4}]}}

{\ displaystyle {\ mathsf {HgI_ {2} + 2KI \ {\ xrightarrow {}} \ K_ {2} [HgI_ {4}]}}}

Application

Preparation of Nessler's reagent .
To obtain tetraiodomercurates of potassium and barium.

Literature

Chemical Encyclopedia / Editorial Board: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1995. - T. 4. - 639 p. - ISBN 5-82270-092-4 .
Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 2nd ed., rev. - M.-L.: Chemistry, 1966. - T. 1. - 1072 p.
Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 3rd ed., rev. - L .: Chemistry, 1971. - T. 2. - 1168 p.
Lidin R.A. and other Chemical properties of inorganic substances: Textbook. manual for universities. - 3rd ed., Rev. - M .: Chemistry, 2000 .-- 480 p. - ISBN 5-7245-1163-0 .
Ripan R., Chetyanu I. Inorganic chemistry. Chemistry of metals. - M .: Mir, 1972. - T. 2. - 871 p.

Mercury iodide

Are common
Systematic name	Mercury iodide (II)
Traditional names	Mercury iodide
Chem. formula	HgI ₂
Physical properties
condition	α - red crystals β - yellow crystals
Molar mass	454.40 g / mol
Density	α - 6,283 β - 6.271 g / cm³
Thermal properties
T. melt.	250; 256; 259 ° C
T. bale.	354 ° C
Chemical properties
Solubility in water	0.006 g / 100 ml
Solubility in ethanol	2.19 g / 100 ml
Solubility in methanol	3.16 ²⁰ ; 6.51 ⁶⁰ g / 100 ml
Acetone solubility	2.1 g / 100 ml
Classification
Reg. CAS number	7774-29-0
PubChem
Reg. EINECS number
Smiles
Inchi
Chebi
UN number
ChemSpider
Security
MPC	air 0,0003 mg / m³
NFPA 704	0 3 0